- Volume 29, Issue 1, 1962

SUMMARY: A survey of the proteolytic bacteria present in the rumens of sheep on different kinds of diets has been made, with special emphasis on the isolation of anaerobic types. The results suggest that proteolytic activity is not confined to a single kind of rumen bacterium, but that it is a variable property possessed by strains of many kinds of bacteria which can be active in the breakdown of other feedstuff constituents. The properties of the bacteria isolated are given.

SUMMARY: Bacteriophage T2r inhibits the division of the host cell Escherichia coli B, immediately after adsorption. Synchronized cells, when infected by phage at the moment of cell division, cannot carry this process to completion. The same effect is exhibited by phage inactivated by ultraviolet light. In contrast, bacteriophage øx-174 allows infected cells to divide before lysis. Determination of the rate of synthesis and final yield of virus showed that synchronized cells from the middle period between two divisions produced the highest burst sizes, whereas the lowest burst sizes were observed in dividing cells.

SUMMARY: Morphological and serological evidence is presented to demonstrate that an organism morphologically identical with Streptobacillus moniliformis is a stage intermediate to the L-form of a strain of Corynebacterium cervicis, that it is serologically closely related to a type culture of S. moniliformis, as well as to strains of Mycoplasma hominis; thus supporting the conclusion that L1, derived from S. moniliformis, and M. hominis have a similar origin, and suggesting that S. moniliformis is an intermediate stage between a Corynebacterium resembling C. cervicis and an L-form.

SUMMARY: Total counts were made of bacterial spore suspensions using counting slides with chamber depths of 0·02 mm. and of 0·10 mm. Sources of error were analysed. In addition to an inherent sampling error, significant variation between counts on replicate slides may result from: (i) variation in the depth of different counting chambers, (ii) variation in the fit of cover-glasses with counting chambers. The use of 0·10 mm. rather than 0·02 mm. depth slides results in a lower estimate of the total count of a spore suspension. The former slides give more reproducible counts; evidence for their greater accuracy has been obtained by a comparison of ‘percentage viability’ of spores determined by counting and by slide-culture techniques.

SUMMARY: Experiments on rat tumours induced by polyoma virus indicate that, although no virus was directly demonstrable in these tumours, at least by the technique used, some of the tumours when set up as tissue cultures were still capable of synthesizing polyoma virus. This faculty disappeared, however, most instances after transplantation in vivo; virus recovery by tissue culture procedures after passage in rats was exceptional. Furthermore, if one draws a parallel between the virus/cell relationship in rat polyoma tumours and the lysogenic system in bacteria, one finds that both phenomena though not exactly similar have many points in common.

SUMMARY: Increased oxygen tension (pO2) caused increased respiration by excised soybean nodales of all ages. The increase took place in two steps, the first maximum occurring at about 50% O2 and the second at 90–100% O2 for actively nitrogen-fixing nodules. With increasing nodule age the first maximum occurred at decreasing pO2 until, when fixation ceased at about 6 weeks, this maximum had disappeared. This effect was more marked at 30° than at 23°. The respiration of bacteroids increased with increasing pO2 with a maximum at 2–3% O2; the curve indicated a simple saturation of the terminal respiratory pathway with O2. Increased pO2 raised nitrogen fixation by excised nodules to a maximum which corresponded to the first maximum of the respiratory response to raised pO2; higher pO2 than this decreased nitrogen fixation. Sliced nodules showed the same effect but the stimulation of fixation at the lower pO2 levels was not as great as with intact nodules. The Michaelis constant (Km ) for nitrogen fixation by intact excised nodules was relatively unaffected by pO2 until this reached the pO2 for maximum fixation when the Km rose sharply. At external pO2 of 80%, oxygen was shown to be a competitive inhibitor of nitrogen fixation.

An explanation of these results is offered; it is suggested that the first part of the nodule O2 consumption/pO2 curves is due to O2 consumption by plant tissue and the second part to O2 consumption by bacteroids. The two components are separated by an O2 permeability barrier. When this barrier permits a rise in the pO2 at the bacteroids, nitrogen fixation is inhibited as oxygen competes with nitrogen for the reducing power of the bacteroids.

SUMMARY: Four wild and two laboratory isolates of Pithomyces chartarum were grown under identical conditions, in submerged and in surface culture; yields of organisms and utilization of medium constituents are reported. Sporidesmin was produced in submerged culture and in surface culture by all the isolates examined but these showed differences of up to at least 100-fold in ability to produce the metabolite. Sporidesmolides were not isolated from cultures which did not sporulate.

SUMMARY: Conditions optimal for the laboratory culture of unpurified Fuligo septica plasmodium were examined. The organism was grown in the laboratory for over 2 years, during which time regular sporulation occurred. Investigation of factors which affected sporulation suggested that this was induced by material present in older cultures; light did not precipitate it. Spore germination occurred readily in the laboratory; some experiments on germination were made. F. septica plasmodium was purified by a migration technique combined with antibiotic treatment. Two-member cultures were established with two yeasts and a Penicillium sp. isolated from plasmodium, and with a baker's yeast. Several other organisms (including Gram-positive and Gram-negative bacteria and yeasts) were not satisfactory as associate organisms in two-member cultures. Satisfactory axenic culture was not obtained, slow growth for a few weeks only being obtained on an autoclaved suspension of baker's yeast.

SUMMARY: L-Cysteine became toxic to the growth of Neurospora crassa (wild, Em 5297a), in the range 1·0–2·0 mM in the culture medium. The specificity of cysteine toxicity was shown by absence of toxicity with other sulphydryl compounds (β-mercaptoethanol, thioglycollic acid, reduced glutathione) and with cysteine metabolites, L-cysteic acid and taurine, under similar conditions. The toxicity of L-cysteine was completely overcome by supplements of S-methyl-L-cysteine and to a marked extent by DL-methionine and DL-homocysteine; partial counteraction of cysteine toxicity was observed with L-serine, DL-tryptophan, DL-alanine, DL-valine, DL-homoserine or DL-threonine. DL-Methionine and S-methyl-L-cysteine counteracted the inhibitory effect of L-cysteine in two N. crassa mutants, namely, methionineless mutant 38706 and cystathionineless mutant 9666.

SUMMARY: A streptomycin-resistant strain of Staphylococcus aureus, which requires haemin for aerobic growth, grew either aerobically or anaerobically in the absence of haemin provided the medium was supplemented with acetate or pyruvate; growth with these organic acids was increased by uracil and purines. The parent drug-sensitive strain grew aerobically without haemin but when grown anaerobically required either uracil or acetate or pyruvate. With both strains mevalonate replaced acetate and was about ten times more active.

The products of glucose fermentation by both strains showed no gross difference, lactate being predominant (about 85% of the glucose carbon); only small amounts of acetate were detected. Under aerobic conditions suspensions of the parent strain oxidized glucose to acetate which accumulated. The mutant strain oxidized glucose to acetate only when previously grown with haemin or when haemin was added to the suspension of organisms. When the organism was grown with acetate in place of haemin, lactate was the predominant product. The ability of the mutant to form sufficient acetate from glucose for biosynthetic purposes is apparently dependent on a functional electron transport chain involving haemoproteins. A nicotinamide-adenine dinucleotide-linked lactate dehydrogenase and a pyruvate oxidizing system are present in extracts of both organisms. The activity of these enzymes in the mutant strain was similar whether the organisms were grown on haemin or acetate.

SUMMARY: Murray Valley encephalitis virus was grown in baby mouse brain and purified. In five out of six experiments, the number of virus particles per chick egg LD50 was 90 ± 50. Fifteen preparations of purified virus were pooled and the pool examined chemically. The nucleic acid content was 7·8%, with bases present in the proportions: adenylic acid, 25·5; guanylic acid, 27·5; cytidylic acid, 21·5; uridylic acid, 25·5. No thymidylic acid was found. The virus preparation contained 11% lipid; phospholipid and total cholestorol were present to 0·8% and 1·6%, respectively, of the virus preparation.

SUMMARY: Tests for decarboxylation of amino acids, oxidation of gluconate, growth in potassium cyanide broth, utilization of malonate and deamination of phenylalanine were applied to 269 strains of aerobic Gram-negative rods, other than members of the Enterobacteriaceae. The results indicated that some of these tests might be of value in the identification of organisms outside this family. The decarboxylase and KCN tests permitted separation of Pasteurella septica from P. pestis and P. pseudotuberculosis. Phenylalanine deaminase was detected in only one of the strains tested. Possible mis-classification of Pseudomonas maltophilia and of the glanders bacillus was suggested.